Question

I lost my friend’s bike, and I really don’t know ________.

A．what should I do

B．what to do

C．how shall I do

D．how to do

Answer 1

B

I really don’t know后如果跟宾语从句，从句要用陈述语序，所以排除A,C；句中不定式to do后缺do的宾语，所以选B。